In the vast low-nutrient—low-chlorophyll (LNLC) ocean, the vertical nutrient supply from the subsurface to the sunlit surface waters is low, and atmospheric contribution of nutrients may be 1 order of magnitude greater over short timescales. Recently, significant experimental, field and modeling work allowed us to better link atmospheric deposition with nutrient availability, ocean productivity, carbon cycling and marine emissions. By improving our understanding on how atmospheric inputs are impacting biological activity and the carbon balance in oligotrophic environments, their representation in biogeochemical models at different timescales and space scales will be better assessed. In particular, processes may be affected by ongoing environmental changes in the ocean such as a decrease in pH and an increase in temperature. This special issue aims at gathering contributions from both experimental and modeling approaches showing how natural or anthropogenic inputs from the atmosphere can impact biogeochemical and ecological processes in the present and future oligotrophic ocean. It will present the results obtained during the PEACETIME (ProcEss studies at the Air-sEa Interface after dust deposition in the MEditerranean sea) cruise conducted in 2017 in the Mediterranean Sea, but the special issue is open to any submissions provided that the subject is consistent with the objectives defined above.

The main value of the paper is to document in-situ observations of mesozooplankton diversity responses to natural Saharan dust depositions in Mediterranean Sea. The dust fertilization of the surface waters induces a rapid dominance of herbivorous zooplankton in the net samples linked to the new primary production. A time lag of 10 days after the dust deposition was necessary to observe the first signs of recovery towards a stable zooplankton community structure.

Residence times of particulate metals derived from aerosol deposition in the Sea Surface Microlayer of the Mediterranean Sea ranged from a couple of minutes (e.g., for Fe) to a few hours (e.g., for Cu). Microbial activity seems to play an important role in in this process and in the concentration and distribution of metals between diferent water layers.

We describe here the objectives and strategy of the PEACETIME project and cruise, dedicated to dust deposition and its impacts in the Mediterranean Sea. Our strategy to go a step forward than in previous approaches in understanding these impacts by catching a real deposition event at sea is detailed. We summarize the work performed at sea, the type of data acquired and their valorization in in the papers published in the special issue.

The arrangement of deep nutrient reservoirs is driven by large scale circulation features, however internal processes could also contribute at long terms.We propose to test this hypothesis in the western Mediterranean Sea, where diapycnal diffusion between intermediate and deep waters is enhanced, ultimately shaping the water column as thermohaline staircases.The estimation of nutrient fluxes induced by these processes showed their contribution to observed spatial pattern of the nutrient stocks.